Teaching pronunciation via food - that's the way. Get your students to bring in a whole bunch of food - some bitter, some sweet, salty, sour, hot etc. Be sure that you previously have read up on where we taste 'sweet' on the tongue, where 'hot' etc (e.g. 'chilli hot' is the very tip). Introduce them to the food, and elicit taste words; then drill with the mouth full (good for a laugh). A quick game of blindfold-tasting (It's sweet and crunchy - might be a biscuit etc.) will practise the vocab. From there, students need to be guided to discover the tongue areas - from this point on you have a ready-made pronunciation vocab-list: to produce /th/, the 'hot' bit of the tongue needs to be just behind the front teeth, /r/ involves the 'hot' bit curling back.... etc. And, once taught, the students never forget it.